The present invention relates to a protection control for a head for recording or reproducing data in a magneto-optical recording/reproducing device.
As is well known in the art, a magneto-optical recording/reproducing device capable of recording or reproducing data in response to light is provided with a head structure such that a laser spot is irradiated through an objective lens onto a recording surface of a magneto-optical disk, and a magnetic head contacts the other surface of the magneto-optical disk on the opposite side of the recording surface, so as to apply a desired magnetic field at a position where the laser spot is irradiated.
Such a head structure is movable (thread feedable) in a radial direction of the magneto-optical disk, so as to trace a spiral recording track on the disk and write or read data at an arbitrary position of the recording track.
The head structure is normally constructed of an optical head for irradiating a laser beam onto a disk surface and a magnetic head for applying a magnetic field to the disk. The optical head and the magnetic head are moved together in the radial direction of the disk.
The optical head includes a focus servo for maintaining a constant distance between the objective lens and the disk surface. It is preferable that the magnetic head is disposed as close as possible with respect to the disk surface, but not to contact the disk surface, for the purpose of applying a large magnetic field.
As a method of maintaining a constant distance between the magnetic head and the disk surface spaced close to each other, it has been proposed that an actuator for the magnetic head and a control device for the actuator similar to the focus servo are provided. However, such a control means causes an increase in weight of the head as a whole and complicates the structure.
To cope with this problem, it is considered to adopt a magnetic head of a flying type as conventionally employed in a recording/reproducing head for a hard disk.
Referring to FIG. 2 which shows such a flying type magnetic head in an enlarged front elevation, an optical head 13 for irradiating a laser spot is located under a disk 11, and an objective lens L incorporated in the optical head 13 is controlled in position by a conventional focus servo technique. A magnetic head provided with a modulation coil 15 is located over the disk 11, and it is normally maintained in slight pressure contact with the disk 11 by an elastic arm 14 or the like for downwardly biasing the magnetic coil 15.
In such a head structure, when the disk 11 is rotated at a high speed in a direction of arrow Q by a motor (not shown), an air stream A is generated on the disk surface, and a flying force is generated by the air stream A to lift the modulation coil 15, thus defining a fine gap d (10 .mu.m) between the disk 11 and a contact surface of the modulation coil 15.
Such a magnetic head is called a flying head. In the flying head, the fine gap d is maintained at a constant value when a rotating speed of the disk 11 is constant. Therefore, even when the modulation coil 15 is small, a magnetic field can be efficiently applied to the disk 11.
However, if the disk is not being rotated at a predetermined speed, the above-mentioned flying force cannot be constantly generated. That is, when the disk is in a stop condition, no flying force is generated. Further, if water or moisture exists on the disk surface, the magnetic head sticks to the disk surface under the stop condition of the disk. When the disk starts to be rotated under the above condition, there is a possibility of damage of the magnetic head or the disk surface.